1. Related Technical Fields
Related technical fields include navigation devices, methods, and programs that perform map matching for navigation.
2. Related Art
On-vehicle navigation devices that find a travel route to a destination and guide the vehicle are widely used. This type of navigation device identifies the current position of the vehicle, displays the vehicle's current position on a map, and provides travel guidance. Types of sensors used for identifying the current position include gyro, vehicle speed pulse, and acceleration sensors, and an estimated path is generated from the sensor information using dead reckoning navigation.
Shape matching of the generated estimated path and road information stored in a DB (database) is performed, and a position where the two coincide is identified as the current position. A current position mark that represents the host vehicle position is displayed at the identified current position. In this case, a position correction is performed so as to move the entire estimated path such that an estimated current position aligns with the current position on the road where the estimated path and the road information coincide. When matching an estimated path based on dead reckoning navigation with a shape based on road information as described above, if the shapes of the estimated path and the road information are compared and coincide, then a match may be made to the wrong position as a consequence.
GPS is used for measuring an absolute position (latitude, longitude) of the vehicle. GPS information is mainly used in sensor learning, but is often not used for position correction during normal updating of the current position. This is because multipath or similar effects, a weakness of GPS, may reduce the accuracy.
Japanese Patent Application Publication No. JP-A-H06-148307 proposes art that performs matching using GPS. According to JP-A-H06-148307, a GPS positioning error is calculated and a circle is set with the positioning location based on GPS as its center and the GPS positioning error as its radius. Candidates outside the circle are removed as possible matches, and only candidates inside the circle are considered as possible matches in order to reduce the processing load.